Synthesis of methyl-substituted pyrano-thiapyrano-, and selenapyrano[2,3-b]pyridines

Abstract

2H-Pyrano-, 2H-thiapyrano-, and 2H-selenapyrano[2,3-b]pyridines containing a methyl group in the α position of the pyridine ring were synthesized by Claisen condensation of the ethyl esters of, respectively, 2-ethoxy-, 2-ethylthio-, and 2-ethylseleno-6-methylpyridine-3-carboxylic acids with ethyl acetate, reduction of the resulting ethyl esters of 2-ethoxy-, 2-ethylthio-, and 2-ethylseleno-6-methylnicotinoylacetic acids with lithium aluminum hydride, and heating of the resulting 2-substituted 3-(α,γ -dihydroxypropyl)-6-methylpyridines with 48% hydrobromic acid.